Jaimini Jyotish is actually called Mahaṛṣi Jaimini Kṛtam Upadeśa Sutram. This Jyotish text was written by Maharishi Jaimini. The key here is in the word Upadeśa meaning advice. Nowadays, Parāśara and Jaimini are categorized as different systems. This is very incorrect. I have made this as different only for clarity, but almost all what Maharishi Jaimini has taught, Parashara has taught in Bṛhat Parāśara Horā Śāstra (BPHS). The word Upadeśa means that Maharishi Jaimini is offering advice on certain verses already taught by Parāśara. It is to be viewed as more granular teachings of certain Parāśara shlokas. To Study Mahaṛṣi Jaimini Kṛtam Upadeśa Sutram, one must be proficient in basics of Parāśara.